Cancer is a serious disease against human health and has become the first disease causing people to die. Currently, people dying of cancer are about 1,400,000˜1,500,000 in China every year, and it is estimated that cancer causes an economic loss of 14 billions every year. Treatment with antitumor drugs is one of the major methods for tumor therapy. Natural products are important resources for the discovery of new antitumor drugs, and lead compounds of many antitumor drugs are obtained from nature, such as vinblastine, vincristine, camptothecin and paclitaxel, etc. However, these compounds need to be structurally modified and improved to be used as clinical antitumor drugs due to their problems in toxic side effects, solubility and stability, etc.
Quinone methide triterpene compounds are a class of natural compounds having antitumor activity. The unique quinone methide structure in the A ring thereof endows these compounds with antitumor activity, but also with easy polymerization, high sensitivity to pH in a solution, and instability under basic or acid conditions so as to easily take place various reactions such as ring-opening, rearrangement, etc. [reference 1: K. Nakanishi, Y. Takahashi and H. Budzikiewicz, Pristimerin. Spectroscopic Properties of the Dienone-Phenol-Type Rearrangement Products and other Derivatives. J. Org. Chem. 30:1729 (1965)]. Natural quinone methide triterpene compounds are fat-soluble, and hardly soluble in water, and thus difficult to be administered intravenously.